The present invention relates to a rubber composition for base tread and a pneumatic tire using the same. Particularly, the present invention relates to a rubber composition for base tread having reduced heat build-up characteristics and excellent reinforcing property, and a pneumatic tire using the rubber composition for base tread.
In recent years, demand for improvement of tire life is increasing, and there are developments such as improvement of abrasion resistance of cap tread rubber and increase of tread width. However, such attempts are now resulting in problems that a tire has increased heat build-up characteristics to cause separation of tread from belt owing to the heat build-up, and that rolling resistance of a tire is increased.
As a means for alleviating these problems, a general technique is to form a two-layer structure tread comprising cap and base, using a low heat build-up rubber for the base tread. However, reinforcing property of a usual low heat build-up rubber is poor, and therefore abrasion resistance decreases when the base tread is exposed at a late stage of abrasion, causing poor abrasion appearance (chipping) or crack at the bottom of the groove. Therefore, the low heat build-up rubber can be only used in such an amount that it is not exposed to the surface even if abrasion occurs, and lowering effect on heat build-up remains small.
In order to meet the demand for long life tires, primal task is to develop a rubber composition having reduced heat build-up characteristics and high reinforcing property, achieving a practical use of low heat build-up tire having a structure with increased base volume.